Evaluation of polymeric Al-modified bentonite for its potential application as ceramic coating

A polymeric Al-modified bentonite (B-OHAl) obtained by intercalation of OH-Al species was used as precursor for mullite-containing coatings. Raw clay and B-OHAl were characterized by X-ray fluorescence (XRF), Infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA). Rheological and electrokinetic behavior of B-OHAl dispersions were optimized by the addition of sodium polyacrylate (NaPA) for its use in dip coating on ceramic substrates. Moderate densification and mullite development of B-OHAl by thermal treatment up to 1200 °C was observed by mercury intrusion porosimetry (MIP), XRD and scanning electron microscopy SEM. NaPA addition on dispersions and an increase in porosity values in substrate led to higher amounts of coating retained in dip coated composites sintered at 1200 °C.